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tions of nitrocellulose have generally been from the thick tough syrup a thread of the Hurrah Snares aren't rrrcu.

MAX FREMERY AND JOHANN URBAN, OF OBERBRUCH, GERMANY.

Passes or MUFACT URING ARTIFEGEAL SELK.

SPECIFICATION forming part of Letters Patent No. 617,009, dated. January 3, 1899.

Application filed February 12, 1898.

To (ZZZ whom it may concern: Be it known that we, MAX FREMERY and J OHANN URBAN, residing in Oberbruch, in the German Empire, have invented certain new and useful Improvements in Processes of ManufacturingArtificial Silk; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

In the manufacture of artificial silk soluemployed, and with a view to imparting greater brilliancy to the product suitable agents, such as oils or the like, have been mixed with these solutions. Owing to the highly-inflammable character of nitrocellulose it becomes necessary either to denitrate the solution or the final product, and this has always proven a most difficult operation, especially when applied to the final product or thread. To avoid this diificulty, it has been proposed to use pure cellulose and convert the same into a tough paste or syrup by treatment with sulfuric and phosphoric acids and then form the threads therefrom. This process has, however, not gone into practical use on account of the impossibility of obtaining fineness and external structure of the naturalsilk fiber. The use of zinc-chlorid solutions of cellulose has also been proposed for the production of threads suitable, after carbonization, for use as filaments for incandescent lamps; but practice has demonstrated the impossibility of obtaining even these comparatively thick threads from such solutions.

After extensive experiments with all of the solutions above referred to we have found it impossible to produce therefrom a thread of such a character as to constitute or which may be held to be a surrogate of the natural-silk fiber, although. threads such as are suitable for carbonization and use as filaments for incandescent lamps can readily be obtained from some of said solutions. All attempts made to obtain a thread of the same degree of fineness as the natural-silk fiber-na'mely, of a thickness of from 0.004: to 0.009 millimeterswith the described solutions have, however, resulted in a failure, because of the im- Serlal No. 670,124. (No specimens.)

equal lengths is a thousand times greater.

than that of the natural-silk fiber. Furthermore, the tenacity and strength of the comparatively thick threads obtainable from zincchlorid solutions of cellulose are very materially impaired in the washing out of the sixty per cent. to eighty per cent. of zinc chlorid generally present. We are not aware that attempts have been made to obtain from these zinc-chlorid solutions a thread as fine as the natural-silk fiber, and if such attempts have been made they must have resulted in failure. Finally, we may state that it has also been proposed to use a cupro-amr'nonium salt solu tion of cellulose in the production of threads,

suitable after proper treatment for use as in-' candescible filaments, by evaporating the solution so as tdproduce a film, which was then cut into strips suitable for conversion into incandescible filaments. This process has, however, likewise found no practical use, owing to the great difiiculty in obtaining the desired result. We may therefore safely state that a fiber of the fineness and appearance of natural silk has never been produced from cellulose solutions. The failureof our attempts in this direction led us to further experiments, which demonstrated that if a cellulose solution capable of being filtered and of the required consistency and homogeneity could be obtained an artificial-silk fiber of a fineness and having the appearance of the natural-silk fiber could be produced. To this end we experimented further with cupro-ammonium salt solutions of cellulose,

because we became convinced that if a solution having the properties referred to could be obtained the problem of the manufacture of artificial silk on a practical and economical basis would be solved, owing to the fact that the solvent might be recovered in a useful form. These experiments finally culminated in a simple and cheap process whereby artificial silk can be produced, the reagents readily recovered in a useful form, and the erwise a final product such as contemplated roundabout methods involving the use of irrevocable and costly reagentssuch as nitric acid, alcohol, ether, and the denitrating agents-avoided. These experiments have also convinced us that the decomposition of the cellulose solution must be avoided; othwould become impossible.

In order that our invention may be fully understood, we will now describe the same in detaiL,

Cellulose of any kind is first freed from fatty constituents by washing it in a weak solution of an alkali. It is then dried and dissolved in a cupro-ammonium salt solution in the proportion of about forty-five grains of cellulose per liter of the-solution, which should contain about fifteen grains of copper per liter, while the proportion of ammoniagas may be ten times as great. The cellulose solution is then filtered either by suction or by centrifugal action and caused to flow through an aperture or apertures of the required degree of fineness into a bath containing a precipitant of cellulose-such as'a weak solution of acetic acid, whereby the cellulose is precipitated in the form of fine threads, the acetic acid combining chemically with the solvent of cellulose-t. e. the cupro ammonium salt, the latter having a greater affinity for the precipitant than the cellulose. The fine threads or fibers thus formed are then wound upon a roller revoluble in the bath, from which roller they are subsequently unwound and wound upon another outside of the bath and at the same time exposed to the action of a warm current of air to dry,

after which the thread is spooled or wound on bobbins.

The cupro-ammonium salt solution of cellulose can be obtained by exposing metallic copper in presence of liquid ammonia to the action of air or of oxygen and, if desired, by addition of an insoluble and more electronegative metal, such as platinum, or under simultaneous use of the electric current, the solution of the cellulose being completed in about eight days. Inasmuch as the solubility of the cellulose decreases as the temperature of the cupro-ammonium salt solution increases, while the decomposition of the cellulose increases with increasing temperatures, the mixture should be kept comparatively cool until the cellulose has been completely dissolved in order to prevent decomposition, for reasons above set forth.

In order to obtain the results aimed at, it is, as above stat-ed, necessary that the solution of cellulose prepared at a suitable temperature to prevent decomposition should be of the properconsistency and perfectly homogeneous. When prepared in about the proportions set forth, the solution will be found to possess the required consistency, and in order to render it perfectly homogeneous We first filter the same through any suitable fabricas, for instance, a woolen fabric or through guncotton, glass wool, or even sand and suction or centrifugal action can be applied for this purpose.

After the thread has been formed as above described and freed from copper and ammonia and removed from the bath the ammonia and copper can be recovered from such bath in a useful form by well-known means. 1

If desired, waste silk can be mixed and dis= solved with the cellulose and substances add ed to the solution that will enhance the brilliancy of the final product without departing from the spirit of our invention.

Having thus described our invention, what we claim as new therein, and desire to secure by Letters Patent, is-

1. The process which consists in dissolving cellulose, without decomposing the same, and causing the solution to fiow in a thread or fiber like stream into a bath containing a precipitant of cellulose, whereby the latter is precipitated from its solution in a thread or fiber like form, for the purpose set forth.

'2. The process, which consists in dissolving cellulose, without decomposing-the same, in a cupro-ammonium salt solution and causing the solution to flow in a thread or fiber like stream into a bath containing a precipitant of cellulose, such as an acetic-acid solution, whereby the cellulose is precipitated from its solution in a thread or fiber like form, for the purpose set forth.

8. The process, which consists in dissolving cellulose without decomposing the same,causin g the solution to flow in a continuous thread or fiber like stream into a bath containing a precipitant of cellulose, whereby .the cellulose is separated from the solution in a thread or fiber like form, winding the thread as it is precipitated within the bath, then unwinding such thread and winding the same outside the bath and simultaneously therewith subjecting the thread to the action of a dry ing agent, substantially as set forth.

4. The process, which consists in dissolving cellulose without decomposing the same, fil tering the solution and causing it to flow in a thread or fiber like stream into a bath containing a precipitant of cellulose, whereby the cellulose is precipitated from the solution in a thread or fiber like form, for the purpose set forth.

5. The process, which consists in dissolving cellulose without decomposing the same, in a cupro-ammonium salt solution, filtering the solution, causing it to fiow in a continuous thread or fiber like stream into a bath containing a precipitant of the cellulose, as an acetic-acid solution, whereby the cellulose is precipitated from its solution in a thread or fiber like form, winding the thread within the bath as it is precipitated, then unwinding such thread and winding the same outside the bath, and simultaneously therewith subjecting' said threa to the action of a drying" agent, substantially as and for the purpofe set forth. 6. The process, which consists in washing the cellulose in a Weak alkali lye, dissolving the cellulose without decomposingthe same, and causing the solution to flow in a thread or fiber like stream into a bath containing a precipitant of cellulose, whereby the latter is precipitated from its solution in a thread or fiber like form, for the purpose set forth.

7. In the manufacture of artificial silk from cellulose, the process which consists in dissolving the cellulose in a co ra-ammonium salt solution at a sufiioiently low temperature 1 to prevent decrease of solubility and decomposition of the cellulose, for the purpose set forth.

In testimony that we claim the foregoing as our invention we have signed; our names in 20 presence of two subscribing witnesses.

- M. FREMERY. J OHANN URBAN.

Vitnesses:

JOHN HEOKMANNS, FRANK M. BRUNDAGE. 

